For some time now I keep getting the Windows auto-updater promping me to upgrade my XP to SP3. When I try to, the update proceeds almost to the end, but then pops up an error message of "Access is denied" and backs out the update. Every time this happens, the system gets more unstable, now crashing (by freezing up) several times per day.
Start again i.e. reinstall? Seriously. I doubt you'll ever get it back to stable again unless you can narrow it down to a particular driver or something. I don't know how much stuff you'd need to set up though.
I just reinstalled a machine on the weekend. Probably about 3 or 4 hours of major set up. By the time you've messed around with this it might just be easier to set up again...
Slight hijack: if I run the SFC (System File Checker) on my SP3 machines, it asks for an SP3 CD which of course I don't have. What should I give it? A slipstreamed CD doesn't work.